1. Field of the Invention
The present invention relates to a windshield and a head-up display system having a projection area, which projects display light of an image displayed on a display device mounted in a vehicle.
2. Description of the Related Art
Recently, with an increase and diversification of information required by a driver during a drive, a projection-type display system called a head-up display (HUD) device is adopted so that information, which is required for increased visibility, is displayed on a windshield as a virtual image. Thereby, a driver can see the foreground of the vehicle through the windshield together with the virtual image, which is superimposed on the foreground.
In such a projection-type display system, a windshield on which a display image from a display device is projected has a non-planar surface. In addition, the curvature and the angle of inclination according to the horizontal plane (or vertical plane) are different depending on the position on the windshield. Therefore the virtual image projected on the windshield is distorted, thereby affecting the visibility of the virtual image.
The applicants propose a vehicle display apparatus described in a patent document 1. The vehicle display apparatus extracts a specific area, which can cancel out the distortion of an image arising from non-plane of the projection area, from a lens having a curved surface having a single radius of curvature. The projection area is regarded as a correction area, and a display light of the image, which is projected on the projection area of a windshield, is transmitted to the correction member. Thereby, the correction of the distorted virtual image can be accurately carried out with the inexpensive correction member.
In the patent document 2, a sectional shape of a specific area of a windshield in a vehicle is formed into an arbitrary place of a prescribed direction constantly. Thereby, a distortion of a virtual image can become small so that a cross-section (or longitudinal-section) is constant in an arbitrary place in an up and down direction (or a right and left direction).
Patent document 1:                Japan published patent application 2002-202475        
Patent document 2:                Japan published patent application 2006-119384        